It is well known in motor vehicles to have a vehicle panel, such as an instrument panel, including an air bag deployment opening through which an inflatable air bag is deployed. The opening is typically closed by a door to normally conceal the undeployed air bag from view. A conventional door is hingedly mounted to the vehicle panel and separable therefrom so that the inflating air bag forcibly moves the door out of the opening to permit deployment of the air bag through the opening.
An air bag assembly includes a housing mounted beneath the opening in the instrument panel and an inflator for discharging gas to inflate the air bag. Upon the vehicle experiencing a predetermined deceleration, the inflator discharges gas so that: the air bag forcibly opens the door and suddenly deploys through the opening. This sudden deployment of the air bag, causes a rapid pressure drop in the housing as the air bag deploys faster than the inflator can discharge gas.
The prior art teaches that the housing may include aspiration apertures therein which are continuously open for communication with ambient air. Thus, the pressure drop in the housing causes ambient air to be aspirated in through the apertures to augment the volume of inflator gas delivered to the air bag. Inflator gas may also be vented out through these open apertures as necessary.
However, the continuously open apertures may permit inflator gas to escape out through the apertures during initial air bag inflation, thereby reducing the inflator gas available to open the door. To compensate for this reduction, an uploaded inflator which discharges greater amounts of inflator gas may be needed, thereby adding cost to the air bag assembly.
The prior art discloses that a closure device, such as a flexible flap attached to the air bag or the air bag itself, may be used to close she apertures to block inflator gas from escaping out through the apertures. The pressure of the inflator gas maintains the closure device against the wall of the housing to cover the apertures during initial air bag inflation. As the air bag deploys out of the housing, the apertures are opened to permit aspiration of ambient air. By using the flexible flap attached to the air bag or the air bag itself as a closure device, the opening of the apertures is completely in response to the movement of the air bag as it inflates.
Thus, it would be desirable to provide an improved air bag assembly in which the apertures are closed when the door is in the closed position, and in which the apertures are opened in response to opening movement of the door, rather than inflation of the air bag, to maximize aspiration of ambient air in through the apertures to augment the volume of inflator gas delivered to the air bag as enabled by the pressure drop in the housing.